FreeBSD : xen-kernel -- x86: Mishandling of SYSCALL singlestep during emulation (942433db-c661-11e6-ae1b-002590263bf5)

high Nessus Plugin ID 95974

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Synopsis

The remote FreeBSD host is missing a security-related update.

Description

The Xen Project reports :

The typical behaviour of singlestepping exceptions is determined at the start of the instruction, with a #DB trap being raised at the end of the instruction. SYSCALL (and SYSRET, although we don't implement it) behave differently because the typical behaviour allows userspace to escalate its privilege. (This difference in behaviour seems to be undocumented.) Xen wrongly raised the exception based on the flags at the start of the instruction.

Guest userspace which can invoke the instruction emulator can use this flaw to escalate its privilege to that of the guest kernel.

Solution

Update the affected package.

See Also

http://xenbits.xen.org/xsa/advisory-204.html

http://www.nessus.org/u?1c306f0d

Plugin Details

Severity: High

ID: 95974

File Name: freebsd_pkg_942433dbc66111e6ae1b002590263bf5.nasl

Version: 3.7

Type: local

Published: 12/21/2016

Updated: 1/4/2021

Dependencies: ssh_get_info.nasl

Risk Information

VPR

Risk Factor: Medium

Score: 5.9

CVSS v2

Risk Factor: Medium

Base Score: 4.6

Vector: AV:L/AC:L/Au:N/C:P/I:P/A:P

CVSS v3

Risk Factor: High

Base Score: 7.8

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Vulnerability Information

CPE: p-cpe:/a:freebsd:freebsd:xen-kernel, cpe:/o:freebsd:freebsd

Required KB Items: Host/local_checks_enabled, Host/FreeBSD/release, Host/FreeBSD/pkg_info

Patch Publication Date: 12/20/2016

Vulnerability Publication Date: 12/19/2016

Reference Information

CVE: CVE-2016-10013

IAVB: 2017-B-0008-S